1. Field of the Invention
The present invention is related to a hand rail driving apparatus of an escalator which drives a hand rail the same direction as steps which move passengers.
2. Description of the Prior Art
The escalator generally includes a driving motor 4, a reducing drive 5 for reducing a turning effect of the motor, a driving chain 6 for transmitting the turning effect of the reducing drive to a driving sprocket 7, and a driving wheel 8 positioned in an upper portion of a machine room 3, as shown in FIG. 1.
Supporting balustrades 2 and the hand rails 1 are mounted on both sides of the escalator for the sake of passengers. Steps 9, on which the passengers board, are fixed in a step chain 10. The steps move along guide rails together with the step chain while being supported by four step rollers, not shown in the figure.
In addition, a driven wheel 11, to which a chain tension device having a tension spring is attached, is mounted in a lower portion of the machine room for preventing deflection of the step chain 10.
Reference number 12 indicates a driving axis for connecting the driving wheels 8 on both side of the escalator.
FIG. 2A to 2C depict several examples of the conventional hand rail driving apparatus.
FIG. 2A shows a hand rail driving apparatus using pressure of a flat belt. A hand rail driving pulley 13 is connected with use of a driving chain 14 to the driving wheel 8 which moves the steps. The hand rail driving apparatus drives the hand rail 1 by exerting pressure of the flat belt 15 on a contacting point with the hand rail of the hand rail driving pulley 13.
FIG. 2B depicts another hand rail driving apparatus using tension. In that apparatus, the hand rail driving pulley 13 is also connected with use of a driving chain 14 to the driving wheel 8 which moves the steps. The hand rail driving apparatus includes a tension roller 19 in the driving chain 14. The apparatus controls tension of the driving chain, thus driving the hand rail.
In the apparatus using the pressure of the flat belt or the tension as described above, the hand rail driving pulley 13 is connected to the driving wheel 8 through the driving chain 14, thus moving the hand rail 1 in the same direction and at the same speed as the step 9. In the hand rail driving pulley 13 used in these types of apparatus, a frictional elastic body 16 which is made of rubber or urethane is provided by surface treatment, thus driving the hand rail with use of tension and friction of the flat belt 15, as shown in FIG. 3A and 3B.
FIG. 2C shows another conventional hand rail driving apparatus using contacting pressure of a roller. In that apparatus, the driving chain 14 transmits power of the driving wheel 8 to tension rollers 17. A roller driving device 18 is rotated by the tension rollers 17, thus driving the hand rails 1 by exerting a constant contacting pressure on upper and lower surfaces of the hand rails 1.
The roller driving device 18 includes a plurality of driving rollers 18a and a plurality of driven rollers 18b which are mounted in a number corresponding to the driving rollers. The hand rail 1 is interposed between the driving rollers 18a and the driven rollers 18b, thus preserving the constant contacting pressure on the upper and lower surfaces of the hand rail 1.
The frictional elastic body 16 or the tension is used for exerting a driving force of the hand rail 1 which is more than a fixed loss by bending resistivity(.epsilon..sup..mu..theta., friction coefficient, .theta.: angle), and a pure friction force(.mu..times.m ) which increase proportionally corresponding to a change in a rise of an escalator.
However, when the rise of escalator increases, the hand rail driving apparatus of the conventional escalator as described above, needs to increase the tension of the flat belt 15 or to increase the contacting pressure between the driving rollers 18a and the driven rollers 18b in order to obtain a required driving force of the hand rail 1. In addition, when increasing the tension and the contacting pressure, it can not only damage the flat belt 15 and the rollers 18a and 18b but also cause damage of the hand rail 1.
Also, the increase of the driving force, that is, the increase of the tension and the contacting pressure causes decrease of the friction coefficient according to change of properties, thus making a normal operation of the hand rail 1 impossible.
On the other hand, in a conventional method of driving the hand rail of the escalator, a moving velocity of the hand rail 1 is determined by diameters of the hand rail driving pulley 13 and the driving roller 18a. However, when the diameters change by the wear of the hand rail 1, the moving velocity of the hand rail 1 is not sufficiently compensated, thus causing problems of depreciating safety and convenience of the passengers.
In addition, when driving the hand rail 1, severe vibrations are generated in the rate of 50-60[gal]. The conventional hand rail driving apparatus also has problems in which the vibration of the hand rail 1 is transmitted to the passengers directly.
Furthermore, because the hand rail 1 is driven by contacting friction of the frictional elastic body 16, the apparatus acts with sufficient driving force only when there is no alien substance between the hand rail 1 and the frictional elastic body 16, i.e., an indoor escalator. However, when rain, dust, and so on are collected therebetween such as in an outdoor location, the friction coefficient for driving the hand rail is decreased, degrading durability and reliance of the hand rail 1. Therefore, there have been needs for correcting the above problems.